The present invention relates to a semiconductor laser light source device, and in particular, to a semiconductor laser light source device that is preferably incorporated in a semiconductor laser module that is used for optical communication or optical measurement and conducts optical coupling between a laser beam and an optical fiber.
As a semiconductor laser module, there exists one that converges a laser beam emitted from a semiconductor laser light source through and thereby forms images on an end of incidence of a fiber. There is in existence one (Patent Document 1) wherein, in the semiconductor laser module of this kind, a shift of focus caused by changes of oscillation wavelength of a semiconductor laser oscillator resulted from temperature changes and a shift of focus caused by changes of refractive index resulted from temperature changes of the light converging lens cancel each other, by forming a diffractive ring-shaped zonal structure on at least one surface of the light converging lens, or by providing a flat sheet lens on which a diffractive ring-shaped zonal structure is formed, separately from the light converging lens, and thereby, fluctuations of output from a fiber can be controlled.    (Patent Document 1)
TOKKAIHEI No. 11-142696
However, in the semiconductor laser module stated above, it is necessary to form, on the light converging lens, a diffractive ring-shaped zonal structure for temperature compensation, which requires high technologies for making of the light converging lens, and a loss of light caused by the diffractive ring-shaped zonal structure cannot be avoided. Further, when the diffractive ring-shaped zonal structure for temperature compensation is formed on the light converging lens, it is difficult to provide another function such as correction of chromatic aberration to the diffractive ring-shaped zonal structure of this kind.
In the semiconductor laser module, when the flat sheet lens equipped thereon with the diffractive ring-shaped zonal structure is provided separately from the light converging lens, the manufacturing cost is raised by an increase of the number of parts, and a loss of an amount of light caused by the flat sheet lens turns out to be reckoned with.
With the background mentioned above, an object of the invention is to provide a semiconductor laser light source device wherein it is possible to realize temperature compensation of a light converging lens simply without relying only on a diffractive ring-shaped zonal structure, and it is possible to exhibit other function such as chromatic aberration correction when the diffractive ring-shaped zonal structure is formed.
Another object of the invention is to provide a semiconductor laser light source device wherein it is possible to realize temperature compensation of a light converging lens without increasing the number of parts.
Incidentally, there have been known optical information recording media including CD, and as a technology to improve recording density of the optical information recording media, there is known a technology called Super-RENS system. In this system, an information recording layer that is closer to an optical disc representing an information recording medium has thereon a structure that generates near field light, and this near field light is used to reproduce information to attain high density of information recording. Specifically, there is known a method to generate near field light by means of a system of a microscopic aperture type or a light-scattering type.